Ribbed core for steel blades



June 10, 1952 c. B. CONWELL RIBBED CORE FOR STEEL BLADES Filed Oct. 14, 1949 INVENTOR L E w N O C .S E? R m w VI B Y E N R O T T A Patented June 10, 1952 UNITED. STATES PATEN 2,600,048 RIBBEp coRnFoR STEEL BL nns Charles B. Conwell, Glastonhury C nn assignor to United Aircraft. Corporation, East Hartford,

0.0 2;! a ca p rat cnof Delaware Application Octpber '14, 1949, Serial lfio. 121, 31? 12 Claims. (01. 170- 159;)

This invention relates to hollow metal propeller blades and more specifically to an improved core construction for hollow steel blades.

It is an object of this invention to provide a core construction for hollow metal propeller blades wherein the stifiness of both the core and the surrounding blade cover is greatly improved.

' It is a further object of this invention to provide a core for a hollow steel blade or the like wherein the core is also hollow and contains at least one spanwise seam along at least a portion of the core thereby forming a plurality of longitudinally extending hollow members which comprise the strength member for the blade. These and other objects of this invention will'become readily apparent from the following detailed description of the accompanying drawing in which,

Fig. 1 is a plan view of a hollow steel blade having a core constructed according to this invention.

Fig. 2 is a cross sectional view taken along the line 2--2 of Fig. 1.

"Fig. 3 is a cross sectional view taken along the line 33 of Fig. 1.

Fig. 4 is a cross sectional view taken along the lined-4 of Fig. 1.

Fig. 5 is a cross sectional view taken along the line 5-5 of-Fig. 1.

Referring to Fig. 1, a hollow steel propeller blade is shown having a hollow core member generally indicated at H) and an outer cover l2 ol v substantially airfoil shape. The core l0 come prises a shank portion 14 and an elongated main portion l6 which is formed from a substantially tubular member and may have its wall thickness tapering toward the tip portion of theblade as shown.

The elongated portion 16 of the core member is partially flattened as shown in Fig. 3 in' order that the core member may more intimately receive the outer blade cover or shell [2 as better seen in Fig. 3. The end of the tubular portion l6 of the core Ill which is to be positioned adjacent the tip oi the blade is closed or? at?!) by completely flattening the tube in this area and seam welding the adjacent surfaces-together.

In orderto increase the stiffness of the core and the blade when finally assembledthe tubular core portion I6 is crimped along its longitudinal axis to the extent that a longitudinal depression generally designated as I8 is formed ineach of the major surfaces of the flattenedtubular member. Thus a depressed surface 30 (Fig. 4) will be formed in the surface32 of the core portion, l6 d T n p s neid e e d 511mm, will be formed in the surface; These depressed sur 2 faces or channels may be formedby passing the core longitudinally between a pair of rollers or may be produced by any form of crimping so that the lowermost portions of the depressions .will. abut each other as, for example. at as shown in Figs. 4v and 5. The abutting. portionsgof the depressions are then seam welded together there-q by forming a longitudinally extending rib gen.-'. erally designated as 44 (Fig. 5). The rib 44 thus. formed provides additional longitudinal land chordwise stiffness while impartingfurther rigid.- ity ina direction transversely of the chord-ofthe blade.

The depression l8 as shown in Fig. .1. extends from the tip end of the core member inboard toward .the blade shank any desirable distance. Depending on the, structural characteristics desired. a plurality of such depressions may be utilized and if further desired, the depressions may extend. for a greater distance along the longitudinal axis of the core to provide added stiffness'toward the inboard end of .the blade.

To complete the blade assembly, the outer cover I2 is wrapped around the core portion l6 so that the major surfaces 32 and 36 of the core portion [Gare in continuous and intimate abutting relationship with the face sideill and the camber side 52,. respectively, of the blade cover l2. The abutting surfaces of the coreportion l6 and the'bla'de covering [2 are firmly secured together by means of brazing or the like. Thetip portion 6001? the blade covering l2 and the trailing edge 62 thereof are formed by seam welding together the adjacent edges of the blade cover I 2.

As a result of thisinvention a hollow blade core construction has been provided forgrea'tly' improving the torsional rigidity of the blade while also improving the outboard flexural stiffness which in turn reduces the flatwise vibratory stresses in the blade. The improved stifiness in the core is especially important in wideblades" where torsional moments are apt'to be high.

Further as a result of this invention an improved blade core construction has been rovided wherein increased strength is providedj at substantially little o'r no increase in Weight. It is to be understood thatthe particular construction described is readily adaptable to other metal blades as well as hollow steel blades. Although only one embodiment of this invention has been illustrated and described herein, it will be apparent that various changes mm: fications maybe made in the confi'guration and em nt of t e com o en alrtSiWiPhefit (19.1. parting-from thescope of this novel concept:

What is desired by Letters Patent is:

1. In a hollow metal propeller blade, a hollow core member having two major, upper and lower spaced spanwise surfaces, an airfoil shaped cover surrounding said core and secured thereto, said cover and said core being in juxtaposed relation, and means for stiffening said blade comprising at least one spanwise depression in each major surface of said core located intermediate the leading and trailing edges of said core said depressions having a chordwise dimension which is less than the chordwise dimension of the adjacent juxtaposed surfaces of the core and cover.

2. In a hollow metal propeller blade, a hollow core member having two major spaced spanwise surfaces, an airfoil shaped cover surrounding said core and secured thereto substantially throughout said major surfaces, and means for stiffening said blade comprising at least one spanwise depression in one of the major surfaces of said core located intermediate the leading and trailing edges of said core, the lowermost portion of said depression being in juxtaposed relation to the other of said major surfaces and fixed thereto continuously along the length of said depression, said depression having a chordwise dimension which is substantially less than the chordwise dimension of the adjacent major surface of said core member.

3'. In a hollow propeller blade, a hollow core member having upper and lower spaced major surfaces, an airfoil shaped cover surrounding said core and secured to said major surfaces, and means for stiffening said blade comprising at least one spanwise depressed portion in each major surface of said core located intermediate the leading and trailing edges of said core, the depressed portion in one of said surface being disposed adjacent the depressed portion in the other of said surfaces, said depressed portions having chordwise dimensions less than the chordwise dimension of the adjacent major surfaces, and means for securing said portions together continuously along their length.

4. A hollow metal propeller blade comprising a tubular core having two spaced apart major surfaces and a sheet metal airfoil forming covering member surrounding and secured to said major surfaces of said core, said core having a fiattened cross section to provide two major sides, and a reinforcing rib for said core comprising opposed spanwise extending channels in said major sides located intermediate the leading and trailing edges of said core, said channels being arranged in abutting relation and secured togather, the chordwise dimension of said channels being less than the chordwise dimension of each of said major sides.

5. In a hollow metal propeller blade, a spanwise core member having two major spaced apart spanwise surfaces, an airfoil shaped cover surrounding said core and secured thereto, said surfaces being in juxtaposed relation with said cover and means for stiffening said blade comprising at least one spanwise depressed surface portion on each major surface of said core located intermediate the leading and trailin edges of said core, the depressed portions on respective surfaces being formed in opposed relation to each other, the chordwise dimension of said portions being less than the chordwise dimension of the adjacent juxtaposed portions of said surfaces and cover, and means for securing said portion together.

6. In a hollow metal propeller blade, a spanwise core member having two spaced major spanwise surfaces, an airfoil shaped cover surrounding said core and secured thereto in juxtaposed relation with a majority of said surfaces, and means for stiffening said blade comprising at least one spanwise depressed surface portion on at least one major surface of said core located intermediate the leading and trailing edges of said core, said depressed portion being juxtaposed relative to and fixed to the other of said major surfaces continuously along its length said portion having a chordwise dimension less than the chordwise dimension of the juxtaposed core and cover.

7. Means for stiffening an aircraft propeller core formed of a tubular metal member having a flattened cross section to provide two major sides spaced from each other comprising, a comparatively narrow central spanwise extending portion of said sides abutting and secured together said portions having a chordwise dimension less than the chordwise dimension of said sides.

8. In a one piece hollow core member for a hollow metal propeller blade having a surrounding cover of airfoil shape secured thereto along a spanwise axis, means for stiffening said core comprising at least one cooperating pair of longitudinal depressions on opposed surfaces of said core located intermediate the leading and trailing edges of said core, with the chordwise dimension of said depressions bein less than the chordwise dimension of the remainder of the core, said cooperating depressions being in juxtaposed relation, and means for securing said depressions together.

9. In a method of making a hollow metal propeller blade, the steps comprising, partially flattening a tubular metal member throughout a major portion of its length to form a core for the blade, forming longitudinal channels in opposed surfaces of the flattened member whereby the lowermost portion of the channel on one surface abuts the lowermost portion of the channel on the opposite surface, securing said abutting portions together to thereby increase the stiffness of said core, surrounding said core with a metal cover of airfoil shape to form the face and camber sides of said blade, and securing said cover to said core along the opposed flattened surfaces of said core.

10. In a method of forming a metal core for a hollow propeller blade, the steps comprising, partially flattening a hollow tubular member along a majority of its length, sealing the end of said tube which will be positioned adjacent the tip of the blade, forming at least one spanwise corrugation in the opposed flattened surfaces of said tubular member so that the depressed portion of the corrugation in one of said flattened surfaces abuts the depressed portion of the corrugation in the other of said surfaces, and securing said abutting portions together.

11. A method according to claim 10 wherein the corrugations are formed to extend fromthe sealed end of said tubular member inboard along a portion of the length of the tubular member.

, 12. In a hollow metal propeller blade, a partially flattened tubular core member comprising a closed tip portion and having an elongated channel formed in opposed cooperating relation in each of the major surfaces of said core intermediate the leading and trailing edges of said core and extending inboard from said tip portion, said channel being formed of sumcient depth so that the bottom of the channel in the one of said major surfaces abuts the bottom of the chan nel in the other of said surfaces, means for securing together the abutting portions of said channels continuously alon the length of the latter, a cover of airfoil shape surrounding said core and having a portion of its inner surface in intimate contact with said major surfaces, the chordwise contact length of said inner surface and said major surfaces being greater than the chordwise dimension of said channels, and means for bonding said cover to said core.

CHARLES B. CONWELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Offutt Mar. 19, 1935 Number Number Number 

